The mechanism of the ¹²C(γ, 3α) reaction for (Li, p)γ-rays has been estimated from a study of 576 stars in nuclear emulsions. By the analysis of the angular distributions and correlation of the α-particles, the multipolarity of the absorption process of (Li, p)γ-rays by the ¹²C nucleus can be explained by the mixture of two sorts of interaction E1 and E2. This result is consistent with Goward and Wilkins’ conclusion, but our experimental data of the angular distribution of the first α-particles show significant forward asymmetry contrary to their backward asymmetry.

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The intensity and the energy spectrum of low energy neutrons at Mt. Norikura (2740 m above sea level and 25°N geomagnetic latitude) were obtained by observing recoil protons with the randomly operated high pressure cloud chamber filled with hydrogen gas at the pressure of 92 atm. The differential energy spectrum for neutrons in the energy range from 1 Mev to 15 Mev was found to be expressed by
(1.2±40%)×10⁻³×E^{−1.25±0.10}cm⁻² sec⁻¹ sterad⁻¹ Mev⁻¹.
The neutron flux is in conformity with what one would expect from the density of thermal neutrons. Connecting the present data with the others which were obtained by many investigations in different energy ranges, the energy spectrum of neutrons ranging from 1 ev to 10 Bev are discussed.

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The intensity of cosmic-ray neutrons has been continuously observed at sea level and mountain.
The value of absorption mean free path of neutron in the atmosphere, deduced from the barometer effect observed at each station, is 139±5 gr/cm², while 136±2 gr/cm² was obtained from the intensity difference between two stations at different altitude.

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To study the anomalous phenomena of so-called impurity band conduction in semiconductors, the electrical properties of nickel doped p-and n-type germanium have been measured from room temperature to liquid air temperature. The energy differences between nickel levels and the edges of conduction and valence bands are so large that the anomalous behaviour was found in the temperature range of liquid air. A systematic study was made for the samples with different carrier concentration in nickel levels, and it was concluded that Hung’s model was succesful to explain qualitatively the systematic change of the electrical properties of these samples. But to understand the experimental facts quantitatively, it seems to be necessary to develop further theoretical and experimental investigations on this problem.

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It has been found out that the local photocurrent is not homogeneous on the periphery of an alloyed germanium p-n junction, but there appear peaks at some positions. These peaks appear even for relatively lower reverse bias voltages and some of them disappear when the voltage is increased. When the bias voltage exceeds certain value, there appears another peak at a new position. There is a remarkable difference among these peaks in the voltage dependency of local photocurrent.
Experimental results on these peaks of photocurrent and other related phenomena are given. In the last section, the results are discussed and a physical picture for the understanding of the actual alloyed junctions is suggested.

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It was reported previously that the bubble raft model under mechanical vibration shows characteristics corresponding to the thermal agitation in the real crystals. With the same device, observations are made on the static as well as the dynamical features of the grain boundary in bubble raft under vibration. In the process of increasing the reduced temperature, the diffused hole (B-type) boundary transforms itself to the dislocation (A-type or C-type) boundary, and vice versa. The transformation temperature varies depending on the angle of misorientation between the grains. In relation to these observations, it is suggested that the marked correspondence between the dislocation theory and the experiment as to the grain boundary energy is but a natural consequence. Preliminary discussions are tried on the molecular mechanism of the transformation between the incoherent and the coherent boundaries, and on the probable causes of the hysteresis effect observed.

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An X-ray tube with a rotating anode and an electro-static lens was constructed, in which the cathode instead of the anode was earthed. Each of the Cu and Fe characteristic rays is obtained without breaking vacuum. An adjustment of position of a camera can be made with quite security, since the total area on the side of a window emitting X-rays is earthed. By this tube, photographs of metals and oxides can be taken in 10 sec and 1min respectively, using Cu radiation filtered by a nickel foil, the voltage and the current being 50 kV and 30 mA respectively, when the electron beam is focussed in an area of 0.25 mm ×0.75 mm by a biasing voltage of about 600 V.

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Polish layers of gold were examined by means of the transmission method of electron diffraction. Line breadths were measured at various stages of polishing. The mean grain size and the mean strain were determined using Hall’s method (Proc. Phys. Soc A 62 (1949), 741) for medium polish layers which produce broad ring patterns. The grain size was also determined from the electron micrograph and from the number of spots on a spotty diffraction ring obtained from a minute region of the specimen. The values obtained from those different methods agree in order of magnitude with each other.
Even at medium stages of polishing, the specimen is polished so heavily as to gain grain size 80 Å and strain 3.6%. The grain size rapidly decreases as polishing proceeds. At the final stage of polishing broad ring patterns change into the halo pattern composed of three haloes. The Bragg spacing corresponding to the most inner halo is 4.08 Å, agreeing with the results obtained by Nonaka and Kohra by the reflexion method (J. Phys. Soc. 9 (1954), 512).

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The formation of the ordered arrangement of the magnetic moments of cations (spin ordering or spin arrangement) in the crystal lattice of the nickel-arsenide type is studied theoretically with the molecular field approximation, taking into account interaction between pairs of cations, which form the first, second or third neighbours in the crystal lattice. Various types of spin arrangement in this structure with two kinds of cations are derived. Based on the results obtained the magnetic properties of the compounds are discussed. The theory is applied as a typical example to the interpretation of the magnetism of the ternary solid solution of manganese-chromium-antimony system.

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The rate of para-ortho conversion in solid deuterium (D₂) is calculated taking two types of interactions, i.e., the magnetic dipole-dipole interaction between D₂ molecules and the coupling between the nuclear quadrupole moments of one D₂ molecule and the total quadrupole moment of the other molecule. It is found that both interactions make about the same contributions to the para-ortho conversion if only the interactions among para molecules are taken into account. However, the ortho molecules with I=2 also interact magnetically with para molecules and convert them into ortho molecules. The calculated conversion rate due to the para-para interactions is found to be 0.01 % per hour times c², where c is the para concentration, while that due to the para-ortho interactions to be 0.01 % per hour times c(1−c), so that the c² termes eventually cancel each other, leaving a total conversion rate which is proportional to c.

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The electromagnetic fields due to the line and surface current flowing in one direction parallel to an interface of two different media are theoretically investigated. Whole problems are dealt with by integral equations of Wiener-Hopf type, and described from a relatively general point of view. Particularly, illustrative cases of a plane wave incident upon a conducting half-plane and a uniform line-current parallel to its rim are studied in detail, and the solutions are given in integral forms. The results may be applied to practical problems.

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The hypersonic viscous flow past a flat plate with suction or injection is dealt with by Kármán-Pohlhausen’s method in special cases when suction or injection velocity proportional to p_B^1⁄2 or x^−1⁄4, especially for the region of strong interaction between the shock wave and the boundary layer, were p_B is the pressure on the plate and x is the distance measured along the plate from its leading edge.
Several numerical examples are given, which shows similar effects of injection to those in the case of incompressible flow that the injection makes all the height of the shock wave, the thickness of the boundary layer and the pressure on the plate larger than those in the case of no injection. On the contrary, in the case of suction no remarkable change both in the height of the shock wave and the pressure on the plate can be seen and only the velocity profile in the boundary layer is affected by the suction.

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Observations were made on the mean and fluctuational velocities of the flow near a wall in turbulent boundary layer with non-zero pressure gradient. The edge of the sub-layer was defined as the maximum-point of the u-distribution curve. Important results obtained are as follows (suffixes 1 and 0 denoting here the values at the edge of the sub-layer and just outside the boundary layer): (i) In the field with constant pressure the curves of \barU⁄\barU₁ versus y⁄δ₁ are similar to those in the field with a fixed value of \barU₁δ₁⁄ν equal to about 165, indicating that the well-known relation between \barU⁄U_τ and yU_τ⁄ν holds near the wall, U_τ being the frictional velocity; (ii) The curve of \barU⁄\barU₁ varies in such a manner that ∂²(\barU⁄\barU₁)⁄∂(y⁄δ₁)² increases with dP₀⁄dx near the wall; (iii) The laminar sub-layer persists until the boundary layer separates and the separation of the sub-layer seems to be equivalent to turbulent separation phenomenon.

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Rigorous solutions are presented of the problem of diffraction of plane electromagnetic waves by an infinitely thin, perfectly conducting infinitely long ribbon and by an infinitely long slit in a plane conducting screen, where the plane of incidence is perpendicular to the edge of the ribbon or slit but arbitrary angle of incidence and polarization. The unique solution satisfying the edge condition is obtained from the electric and magnetic type Hertz vectors, each of which has one scalar component, by the method of expansion in the hypergeometric polynomial. The expressions of the scattering coefficient, transmission coefficient, electric current on the ribbon, electric field in the slit, electric field at the distant place are obtained as a function of ka=2πa⁄λ.

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Variational method is applied to derive two inequalities giving rigorous upper and lower bounds for the initial slope B₀=−\varphi′(0) of the ordinary Thomas-Fermi function \varphi(x), the solution of the non-linear equation
\varphi″=x^−1⁄2\varphi^3⁄2
with the boundary conditions
\varphi(0)=1, \varphi(∞)=0.
Application of these formulas using simple trial functions leads to the estimate
1.5865≤B₀≤1.5883.

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In the customary method of electro-machining of hard metals, it is necessary to initiate some condenced discharges or quenched sparks between the metal to the machined and the tool by incomplete contracts or repeated contacts, where the tool must be kept as the cathode in the circuit of direct current.
In the present method, an ordinary alternating current is used, superposed with some adequate high frequency electric oscillations. The metal and the tool are dipped in water and they are adjusted to keep a certain small separation. Thus, we can initiate favorable quenched discharges in every half cycle, in which the metal is in positive potential.
A merit of the present method is that the developments of any cracks in the machined surface are perfectly prevented even for hard metals, such as tungsten. The time required for drilling a tungsten plate of 3 mm in thickness by a tungsten rod, 1.54 mm in dia., is 4 minutes resulting a hole 1.75 mm in diameter. Screw cutting through a quenched steel plate is proved successful by choosing a brass external thread as a tooling electrode. The mechanism of electro-mechanical machining due to quenched discharges is explained qualitatively; the drilling effect being ascribed to electric attraction working on the melt of the plate, and the consumption of the electrode to a bluster effect of positive ions.

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Analysing the photographs of the ricochet motion, the following results were obtained. (1) The mean hydrodynamical impulsive force is practically independent of the incident angle except for the blunt head projectile. (2) The horizontal component of the force becomes smaller as the incident angle increases and the projectile becomes hard to ricochet as the component nears zero. (3) The point of application of the force recedes as the incident angle increases. (4) The vertical velocity component of the projectile after the ricochet is generally greater than that before.
Furthermore a coefficient of retardation, a coefficient of ricochet, and a coefficient of slip were newly introduced in order to compare the ricochet motion with the motion of repulsing upon a solid wall.

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